The cholesterol-lowering drugs statins may also slow the onset of Alzheimer's disease, according to US researchers who examined the brains of 110 elderly people after they died. They found the brains of patients who had not taken the drugs were more likely to show signs of the disease.

Previous studies have suggested that statins have a protective effect against the brain-wasting disease, but the science is contradictory. "Our study is the first to compare the brains of people who had received statins with those who had not," said Gail Li at the University of Washington.

Around 500,000 people in the UK have Alzheimer's, with around one in 20 of those aged over 65 affected. The risk increases with age and by 85 nearly half of people have developed the disease. Statins are drugs that are thought to prevent heart attacks and strokes by reducing the level of the "bad" LDL cholesterol in the blood. They have been hailed as "wonder drugs" because they have few side-effects and can be prescribed for long periods. They have even shown promising results against diseases such as rheumatoid arthritis and multiple sclerosis.

Dr Li and her colleagues took advantage of an existing study into the health of older people to investigate whether statins had an effect on Alzheimer's disease progression. More than 2,500 volunteers had originally been recruited with no health problems in 1994.

The team was given access to the brains of 110 patients who had given permission for their organs to be used in research. Of these, 36 had received at least three prescriptions for statins.

The team found after dissecting the brains that these individuals were less likely to have neurofibrillary tangles - markers of Alzheimer's progression.

"To our knowledge, this is the first study demonstrating an association between statin exposure and neuropathologic changes associated with Alzheimer's disease," the team write in the journal Neurology today.

"These results are exciting, novel, and have important implications for prevention strategies," said co-author Eric Larson, the executive director of the Group Health Centre for Health Studies. However, he stressed that the finding would need to be confirmed.